These days, a liquid crystal display device having a function of displaying images in a three-dimensional manner (hereinafter may also referred to as “displaying 3D (three-dimensional) pictures”) in addition to a function of displaying images not in a three-dimensional manner (hereinafter may also referred to as “displaying 2D (two-dimensional) images” are in practical use.
As technologies for displaying three-dimensional pictures, an active shutter system, a naked-eye lenticular system, a patterned retarder system (polarization system, which is also called a PR system), and so on, are known. In any of the systems, a right-eye image is presented only to the right eye of a user, and a left-eye image is presented only to the left eye of the user, thereby enabling the user to view the images three-dimensionally.
In a liquid crystal display device using the active shutter system, right-eye frames (R frames) and left-eye frames (L frames) are alternately displayed. A user views images displayed on the liquid crystal display device with 3D glasses having a right-eye lens and a left-eye lens which perform a shutter operation in synchronization with the switching of the L frames and the R frames, thereby viewing the images three-dimensionally.
In a liquid crystal display device using the naked-eye lenticular system, a right-eye image and a left-eye image are respectively presented to the right eye and the left eye of a user via a lenticular lens formed on the front side of a liquid crystal panel. This enables the user to view the images three-dimensionally without the need to use 3D glasses.
In a liquid crystal display device using the patterned retarder system, a right-eye image is displayed by using pixels defined by odd-numbered horizontal scanning lines, while a left-eye image is displayed by using images defined by even-numbered horizontal scanning lines.
The patterned retarder system will be discussed more specifically below with reference to parts (a) and (b) of FIG. 19 and FIG. 20. Part (a) of FIG. 19 is an exploded perspective view illustrating a backlight unit 50, a liquid crystal panel 60, and a patterned retarder 70 included in a known liquid crystal display device using the patterned retarder system.
The backlight unit 50 supplies backlight to the liquid crystal panel 60 from the back side of the liquid crystal panel 60. On the liquid crystal panel 60, pixels defined by horizontal scanning lines (lateral-direction scanning lines) HL1 through HLN (N is the total number of horizontal scanning lines) and vertical scanning lines (longitudinal-direction scanning lines) VL1 through VLM (M is the total number of vertical scanning lines) are formed. The liquid crystal panel 60 controls the orientation of a liquid crystal included in each pixel, thereby making it possible to control the transmittance of backlight to be supplied to each pixel. Additionally, the liquid crystal panel 60 displays a right-eye image by using pixels defined by the odd-numbered horizontal scanning lines HL1, HL3, and so on, and displays a left-eye image by using pixels defined by the even-numbered horizontal scanning lines HL2, HL4, and so on.
The patterned retarder 70 is a retarder plate unit having a length in the direction of the horizontal scanning lines, and includes two types of retarder plates RR and RL having characteristics different from each other. The retarder plates RR convert linearly polarized light into right-handed circularly polarized light, while the retarder plates RL convert linearly polarized light into left-handed circularly polarized light. As shown in part (a) of FIG. 19, the retarder plates RR are disposed on the front side of the pixels defined by the odd-numbered horizontal scanning lines HL1, HL3, and so on, while the retarder plates RL are disposed on the front side of the pixels defined by the even-numbered horizontal scanning lines HL2, HL4, and so on.
Accordingly, a right-eye image to be displayed by using pixels defined by the odd-numbered horizontal scanning lines is represented by light which is right-handed circularly polarized after passing through the patterned retarder, while a left-eye image to be displayed by using pixels defined by the even-numbered horizontal scanning lines is represented by light which is left-handed circularly polarized after passing through the patterned retarder.
Part (b) of FIG. 19 shows 3D glasses 80 used in the patterned retarder system. As shown in part (b) of FIG. 19, the 3D glasses 80 include a right-eye lens and a left-eye lens. The right-eye lens transmits only right-handed circularly polarized light, while the left-eye lens transmits only left-handed circularly polarized light. Accordingly, by using the 3D glasses 80, among images displayed on a liquid crystal display device, the user is able to view right-eye images displayed by using pixels defined by the odd-numbered horizontal scanning lines only with the right eye, and views left-eye images displayed by using pixels defined by the even-numbered horizontal scanning lines only with the left eye, thereby making it possible to view the images three-dimensionally.
A liquid crystal display device using the patterned retarder system can also display 2D images by using both of pixels defined by the odd-numbered horizontal scanning lines and pixels defined by the even-numbered horizontal scanning lines. In this case, the user simply views images displayed on the liquid crystal display device without using the 3D glasses.
The 3D glasses 80 used in the patterned retarder system do not need electrical control, which is necessary for 3D glasses used in the active shutter system. Thus, the 3D glasses 80 can be implemented with a simple structure.
On the other hand, however, in the patterned retarder system, it is known that a phenomenon called crosstalk occurs mainly due to a limited thickness of a glass layer forming a liquid crystal panel.
The crosstalk is the following phenomenon occurring, for example, when the user views a liquid crystal panel from the obliquely top side or the obliquely bottom side. Part of a right-eye image to be displayed by using pixels defined by odd-numbered horizontal scanning lines passes through left-eye retarder plates disposed on the front side of pixels defined by even-numbered horizontal scanning lines and is then viewed, and part of a left-eye image to be displayed by using pixels defined by the even-numbered horizontal scanning lines passes through right-eye retarder plates disposed on the front side of pixels defined by the odd-numbered horizontal scanning lines and is then viewed. Accordingly, the right-eye image is mixed into the left-eye image represented by left-handed circularly polarized light, and the left-eye image is mixed into the right-eye image represented by right-handed circularly polarized light.
Hitherto, the configuration in which the occurrence of crosstalk is suppressed by forming black matrixes and black stripes along horizontal scanning lines in a liquid crystal panel and in a patterned retarder, respectively, is known.
FIG. 20 is a sectional view, along vertical scanning lines (longitudinal direction), of the backlight unit 50, the liquid crystal panel 60, and the patterned retarder 70 included in a known liquid crystal display device, and illustrates an area around pixels defined by an n-th horizontal scanning line and pixels defined by an (n+1)-th horizontal scanning line. FIG. 20 illustrates the liquid crystal panel 60 and the patterned retarder 70 configured in which the occurrence of crosstalk is suppressed by the use of black matrixes and black stripes.
As shown in FIG. 20, the backlight unit 50 is disposed at the back side (the left side in FIG. 20) of the liquid crystal panel 60, and the patterned retarder 70 is disposed at the front side (the right side in FIG. 20) of the liquid crystal panel 60. The liquid crystal panel 60 includes a first polarizing sheet 60a, a TFT-Glass 60b, a TFT substrate 60c, a color filter 60d, a CF-Glass 60e, and a second polarizing sheet 60f. 
As shown in FIG. 20, in the TFT substrate 60c, a black matrix BM is formed between a pixel Pn defined by the n-th horizontal scanning line and a pixel Pn+1 defined by the (n+1)-th horizontal scanning line. Moreover, at the front side of the black matrixes BM, black matrixes BM′ are formed within the color filter 60d, and black stripes BS are formed within the patterned retarder 70.
By using such black matrixes and black stripes, as shown in FIG. 20, if the angle between the direction of a normal to the liquid crystal panel 60 and a viewing direction is within α degrees in the direction of the vertical scanning lines, it is possible to suppress the occurrence of crosstalk.
With this configuration, however, the provision of black matrixes and black stripes decreases the aperture, thereby causing a problem that the brightness of images is reduced.
NPL 1 discloses a technology for suppressing the occurrence of crosstalk without using black stripes by dividing each pixel into two sub pixels (an upper sub pixel and a lower sub pixel) in the direction of vertical scanning lines. In this technology, when displaying a 2D image, a data voltage for displaying an image is supplied to both of the sub pixels, and when displaying a 3D image, a data voltage for displaying an image is supplied to only the upper sub pixel, while a data voltage for displaying black is supplied to the lower sub pixel. The lower sub pixel to which the data voltage for displaying black is supplied functions as a black matrix.
According to the technology disclosed in NPL 1, therefore, the brightness of images is not reduced when displaying a 2D image. When a 3D image is displayed, it is possible to suppress the occurrence of crosstalk by black matrixes.